Extrusion press for the treatment of plastic materials



April 1935- o. LEFNAER 1,997,525

EXTRUSION PRESS FOR THE TREATMENT OF PLASTIC MATERIALS Patented Apr. 9, 1935 UNITED STATES EXTRUSION PRESS FOR THE TREATMENT OF PLASTIC MATERIALS Otto Lefnaer, Vienna, Austria Application April 7, 1933, Serial No. 665,008 InAustria April 16, 1932 5 Claims.

Heretgfore screw presses, roller presses and lately eccentric presses were used for the treatment of plastic materials, particularly clay or clayey materials, by which the plastic material is pressed into the mouthpiece of the press by slides guided in slots.

The screw press possesses the drawback that a very considerable expenditure of force is necessary for its operation and further the extruded string of material is of S- and annular shape. However roller presses exert an insumcient pressure in view of the unfavorable drafting angle. The eccentric presses possess the drawback, that parts of the press which move relatively to one another are subjected to the full pressure of the press, whereby the material still is forced between the same and, owing to its sandy condition, is the cause of an increased expenditure of power and wear.

Roller presses of particular shape, in which a roller is arranged eccentrically within a moldring, are employed for the manufacture of bricks from powdery and binding raw materials, said roller receiving the powder and forces the same at high pressure into the mold-ring, from the side of which the brick is removed hereafter.

The extrusion press according to the present invention relates to that class of presses in which the smaller drum or roller of two drums or rollers rotating in the same direction of rotation, is mounted eccentrically, within the larger drum, and the essential feature of the present press consists in that the outer drum is provided with sieve-like or grating-like openings or recesses through which the material, seized by the two drums, is pressed into the mouthpiece of the press; the surface of said inner drum being smooth, fluted, grooved or toothed.

Further the inner drum may be provided with extensions or projections which, during the rotation of the drums, mesh with the webs of the recessed drum.

Afurther feature of the present invention consists in subjecting the space, through which the material to be treated passes and which is located between the inner drum and the recessed drum, to the actionof a pressure below atmospheric, in order to de-air said material.

Further the construction of the extrusion press can be simplified by replacing the rotary inner drum by a drum-shamd or tempering displacement member which is mounted eccentrically and immovably within'the recessed outer drum.

Some modes of carrying out the present invention are illustrated by way of example on the accompanying sheet of drawing in which all views .are shown in longitudinal section.

Fig. 1 shows a press in which the inner drum is provided with cam-shaped extensions.

Fig. 2 is a view of a press with a. smooth inner drum.

Fig. 3 shows an extrusion press in which the arrangement of the drums is particularly suited for the de-airing of the material to be treated.

Fig. 4 shows an extrusion press with an immovable displacement member of crescent shape in cross section.

The presses'illustrated in Figs. 1, 2 and 3 essentially consist of two drums a and b, arranged within one another in a casing d and rotating in the same direction of rotation at the same speed or at different speeds, the shell of the larger drum a being provided with sieve-like or grating-like openingsor recesses, while the inner drum b is provided with cam-shaped extensions (Fig. 1) or with a smooth surface (Fig. 2) or with teeth (Fig. 3). The material between the drums a and b is seized and drawn between the latter and pressed out through the openings or recesses of the outer drum and into the mouthpiece e of the press. Preferably both drums are rotated. However if desired one drum only, preferably the outer drum a, is rotated this being the case particularly if-no part of the inner drum b contacts or engages the outer drum in any position. In this case the inner drum is rotated solely by the forward moving material contained between both drums.

In order to prevent unnecessary friction, particularly in the event of a toothed drum or roller 12, it is of advantage to prevent contact between the two drums a and b or between their teeth in any position, solely some kind of labyrinth packing being formed which prevents the backward movement of the plastic material.

In many cases it is of advantage that the grating of the drum a consists of webs which at their outer part are inclined in the direction opposed to the direction of rotation, so that the plastic material may slide ofi.

The material may be fed into the press from the sides of the drum a or through its shell, whereby it is of advantage to use a dragging roller 0.

Liquid rinsing may be resorted to, in order to reduce the friction at the walls.

The described extrusion press is employed for the preparation of clay or like materials, if the latter are forced through conveniently narrow clay more compact and dense.

slits or sieve-like recesses and, without further pressure, are subjected to further treatment.

Usually the drum a with the recessed shell and the inner drum 1: are driven, but it is quite sumcient to drive one drum only, preferably the outer drum, while the extensions or teeth of the inner drum b (Fig. 3) enter the recesses of the outer drum a and mesh with the webs of the latter, and consequently the inner drum is positively rotated by the outer drum.

In a more simple construction of the press it is quite suflicient to arrange immovably the inner drum b within the drum a; Thus the inner drum is not rotatable and therefore the material to be treated is drawn into the wedge-shaped space between the rotating drum a and the fixed inner drum b solely by the action of the rotating recessed outer drum and is pressed through the openings in the shell of thelatter and into the mouthpiece of the press. Of course now it is not necessary to make the inner drum of cylindric shape, because the same may be of any convenient even of non-circular shape. As shown in Fig. 4, the inner displacement member b may be of crescent shape.

Finally the displacement member may be dispensed with. The materialis compressed solely by the rotating drum a provided with the recessed shell, whereby the advanced dragging drum feeds the material to be treated into the recesses of the drum a, the latter seizing said material and pressing it through its interior into the mouthpiece of the press. In this case preferably drums of large dia eters are used, in order to reduce the drafting angle and the slip of the material to be drawn-in.

In order to reduce the slip it is of advantage to drive in all constructions the dragging drum 0 at a higher speed than the recessed drum a and to make the dragging drum not smooth but rough, fluted or toothed, whereby the teeth may enter into the recesses of the drum a.

It is known to subject the material to the action of a pressure below atmospheric in order to de-air the same and render the string of Thereby it has been necessary to divide, by separate devices, the material for instance into a number of thin long strings, before said material enters the screw of the press. In the press according to the present invention, the de-airing is carried out during the normal manufacture in that the recesses or openings of the drum a are very narrow, so that the material fed by the dragging drum 0 enters the recessed drum a in a finely divided state.

The material can be subjected to a pressure below atmospheric during its passage through the space 1 between the inner drum 1) and the recessed drum a and before it enters the mouthpiece of the press. As shown in Fig. 3 the material to be treated is supplied to the recessed drum a at a place where not the greatest eccentricity is present between said drum a and the inner drum b, so that the material is partly relieved by the operation of the press. At the same time it is of advantage to provide the inner drum 1) with projections producing the labyrinth packing.

What I claim is:-

1. Extrusion press for the treatment of plastic materials, comprising in combination a casing with an inlet and a mouthpiece for the discharge of the material, a drum fitted rotatable in said casing, openings in the shell of said drum for the passage of the material through said shell, and a compression member arranged eccentrically within said drum-and forcing out the material through the openings in the shell of the drum and into the mouthpiece of said casing.

2. Extrusion press for the treatment of plastic materials, comprising in combination a casing with an inlet and a mouthpiece for the discharge of the material, a drum fitted rotatable in said casing, openings in the shell of said drum for the passage of the material through said shell, and a rotatable compression member arranged eccentrically within said drum and forcing out the material through the openings in the shell of the drum and into the mouthpiece of said casing.

3. Extrusion press for the treatment of plastic materials, comprising in combination a casing with an inlet and a mouthpiece for the discharge of the material, a drum fitted rotatable in said casing, openings in the shell of said drum for the passage of the material through said shell, and a rotatable compression member provided with extensions on its shell arranged eccentrically within said drum and forcing out the material through the openings in the shell of the drum and into the mouthpiece of said casing.

4. Extrusion press for the treatment of plastic materials, comprising in combination a casing with an inlet and a. mouthpiece for the discharge of the material, a drum fitted rotatable in said casing, openings in the shell of said drum for the passage of the material through said shell, the walls bounding said openings being inclined towards the outside in the direction opposed to the direction of rotation of said drum, and a compression member arranged eccentrically within said drum and forcing out the material through the openings in the shell of the drum and into the mouthpiece of said casing.

5. Extrusion press for the treatment of plastic materials, comprising in combination a casing with an inlet and a mouthpiece for the discharge of the material, a drum fitted rotatable in said casing, openings in the shell of said drum for the passage of the material through said shell, a displacement member arranged eccentrically within said drum and forcing out the material through the openings in the shell of the drum and into the mouthpiece of said casing, and a vacuum space left between said drum and said compression member.

OTTO LEFNAER. 

